Barb Fitting / Regulator Cap / Connection

What is the barb fitting in the regulator cap used for?  How and where should it be connected if I  use it, and what should be done with it if I don’t?

All Aeromotive carburetor bypass regulators allow vacuum or boost referencing at a 1:1 ratio. For forced induction "blow through" setups, reference the regulator to positive pressure via the carburetor box or hat, not the manifold. For naturally aspirated or roots supercharged engines, leave the port open to atmosphere.

On naturally aspirated alcohol-fueled engines, referencing vacuum can lower idle pressure and increase it at wide-open throttle by connecting the regulator to the intake plenum beneath the carburetor.

For more details, ask to speak to a Tech.